This is a proposal to study the mechanisms by which puberty is induced in the female rat. To this end a number of studies are proposed as follows: First, further studies will be made of the maturational changes in both the negative and positive feedback of gonadal steroids during development. Second, further studies will be performed of the physiology of the hypothalamic-pituitary-gonadal axis during the infantile period. Third, studies on the development of the neural control of gonadotropin secretion will be carried out with particular reference to the role of prostaglandins in the induction of puberty. Fourth, further studies will be made of the role of prolactin and GH on the onset of puberty. Fifth, studies will be conducted to determine the nature of the factors involved in underfeeding-delayed puberty. Sixth, electrophysiological studies will be made of the maturational changes in the response of hypothalamcc neurons to gonadotropins and prolactin.